1. Field of the Invention
The present invention relates to an improvement of a lens barrel mechanism which includes a bellows-shaped unit for performing light blocking and dust proof, and which is capable of being installed to a camera and the like.
2. Related Background Art
In conventional collapsible mount type camera lens barrels and zoom type camera lens barrels, there have been proposed cameras in which an expandable and contractible bellows-shaped member for performing light blocking and dust proof is provided between optical units or driving mechanisms for the purposes of preventing leakage of light and entering of sand and dust through between a variety of kinds of optical units movable in the optical axial direction, or driving mechanisms for moving these optical units in the optical axial direction.
As a method for fixing the bellows-shaped member, as disclosed in U.S. Pat. No. 6,195,212 and Japanese Patent Application Laid-Open No. 2000-147352, it is general to use a mechanism in which front and rear ends of the bellows-shaped member are fixed to respective optical units or driving mechanisms, and the bellows-shaped member is moved interlocking with relative movement in the optical axial direction between these units or mechanisms while the entire length of the bellows-shaped member is changed.
Further, in Japanese Patent Application Laid-Open No. 2000-347085, an end portion of a bellows-shaped member on an object side is fixed to a frame of a lens barrel, but the other end on a side of an image surface is only brought into contact with a flange portion of a lens supporting frame. In the apparatus disclosed in this Japanese reference, the bellows-shaped member is formed of an elastic rubber, and the bellows-shaped rubber member is assembled by compressive charging, using its rubber elasticity, such that its contact with the flange portion cannot be released even in the event that the lens supporting frame is moved in the optical axial direction relative to the frame of the lens barrel, due to expansion or contraction of the bellows-shaped rubber member in accordance with the relative movement.
In recent collapsible mount type cameras and zoom type cameras, however, downsizing increasingly advances, and it is accordingly essential to reduce sizes and thicknesses of individual components of the camera. On the other hand, a large zoom magnification is needed. Accordingly, the following lens barrel structure is required. In such a lens barrel structure, various optical units and driving mechanisms for moving these optical units in the optical axial direction can be largely moved while small components are used. In such a lens barrel structure, it is naturally inevitable for some components to be moved largely relative to each other (the amount of a distance between these components is largely changed).
As the downsizing proceeds as discussed above, a space for containing the bellows-shaped member in the camera decreases. Accordingly, the length of the bellows-shaped member in its contracted state needs to be reduced, as the result of which the length of the bellows-shaped member in its expanded state is also liable to decrease.
Therefore, in the construction in which both opposite ends of the bellows-shaped member are fixed as in the above-discussed U.S. Pat. No. 6,195,212 and Japanese Patent Application Laid-Open No. 2000-147352, it is difficult to satisfy required amounts of relative movement of the optical unit and the driving mechanism to which ends of the bellows-shaped member are fixed.
Further, in such a construction as disclosed in the above-discussed Japanese Patent Application Laid-Open No. 2000-347085, the amount of the relative movement is not restricted since one end of the bellows-shaped member is only put under a contact condition while the other end thereof is fixed. However, in the event that the components are spaced from each other more than a freely-expanded length of the bellows-shaped member, it is likely that the bellows-shaped member cannot achieve functions of light blocking and dust proof.